Laser processing head, laser processing apparatus, and method for manufacturing metal product

Abstract

A laser processing head (116) is provided with: an aberration optical system that generates aberration and is disposed at a position within a range in which laser light (144) irradiated toward an object to be processed expands in the propagation direction of the laser light (144); and a collimating optical system that propagates the laser light (144). In the aberration optical system, a central region, which is a region having a distance from the central axis of the aberration optical system equal to or less than a boundary value, does not have refractive power, or the absolute value of the refractive power is equal to or less than 1 / 10 of the refractive power of the collimating optical system. A peripheral region, which is a region in which the distance from the central axis exceeds the boundary value, in the aberration optical system has a light-focusing characteristic in which the distance between the aberration optical system and the focal point of a light ray becomes shorter as the position of the light ray is farther from the central axis when the light ray parallel to the central axis is incident on the peripheral region.

Description

Technical Field

[0001] The present disclosure relates to a laser processing head of a laser processing device for processing an object by partially melting the object through irradiation with laser light, a laser processing device, and a method for manufacturing a metal product. Background Art

[0002] In recent years, near-infrared lasers such as fiber lasers, YAG (Yttrium Aluminum Garnet) lasers, and direct diode lasers (DDL) that output laser light in the near-infrared region have been developed with higher focusing and higher output, and laser processing devices using near-infrared lasers as light sources have been developed.

[0003] Patent document 1 discloses a laser processing head having an optical system composed of a first lens for focusing laser light and a second lens arranged on the same optical axis as the first lens. In the optical system described in Patent document 1, a first region of the second lens located on the optical axis has no lens characteristics, and a second region of the second lens surrounding the first region diverges the laser light.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2014-73526 Summary of the invention

[0005] Problem that the invention aims to solve

[0006] In the conventional laser processing head described in Patent Document 1, the energy intensity of the portion of the laser beam that is away from the optical axis, i.e., the peripheral portion, may change due to changes in the divergence angle of the laser beam incident on the optical system. When the energy intensity of the peripheral portion changes, the processing becomes unstable due to unfavorable conditions such as the instability of the keyhole formed in the processing object or the generation of spatter. Therefore, in the conventional laser processing head, there is a problem that the processing sometimes becomes unstable.

[0007] The present disclosure has been made in view of the above circumstances, and an object of the present invention is to obtain a laser processing head capable of realizing stable processing.

[0008] Solutions for solving problems

[0009] In order to solve the above-mentioned problems and achieve the purpose, the laser processing head involved in the present disclosure comprises: an aberration optical system, which is arranged at a position within the range in which the laser irradiated toward the processing object expands in the propagation direction of the laser, and generates aberration; and a collimation optical system, which propagates the laser. The area in the aberration optical system whose distance from the central axis of the aberration optical system is less than the boundary value, that is, the central area, has no optical focal length, or the absolute value of the optical focal length is less than 1 / 10 of the optical focal length of the collimation optical system. The area in the aberration optical system whose distance from the central axis exceeds the boundary value, that is, the peripheral area, has a focusing characteristic in which, when a light ray parallel to the central axis is made incident on the peripheral area, the farther the position of the light ray is from the central axis, the shorter the distance between the aberration optical system and the focus of the light ray is.

[0010] Effects of the Invention

[0011] The laser processing head according to the present disclosure has an effect of enabling stable processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the first diagram for explaining the definition of lateral aberration in the first embodiment.

[0013] Figure 2 This is a second diagram for explaining the definition of lateral aberration in the first embodiment.

[0014] Figure 3 This is a diagram showing the structure of a laser processing device according to a first example of Embodiment 1.

[0015] Figure 4 This is the first diagram for explaining the relationship between the laser processing state and aberration in the first embodiment.

[0016] Figure 5 This is the second diagram for explaining the relationship between the laser processing situation and aberration in the first embodiment.

[0017] Figure 6 The third diagram is used to explain the relationship between the laser processing situation and aberration in the first embodiment.

[0018] Figure 7 Yes means Figure 4 Diagram showing the beam shape of the laser.

[0019] Figure 8 Yes means Figure 5 Diagram showing the beam shape of the laser.

[0020] Fig. 9 Yes means Figure 6 Diagram showing the beam shape of the laser.

[0021] Fig.10This is a diagram showing the structure of a laser processing device according to a second example of the first embodiment.

[0022] Fig.11 This is a diagram for explaining changes in lateral aberration caused by moving the aberration lens in the second example of the first embodiment.

[0023] Fig.12 This is a diagram showing the structure of a laser processing device according to a third example of the first embodiment.

[0024] Fig.13 This is a diagram for explaining changes in lateral aberration caused by moving the aberration lens in the third example of the first embodiment.

[0025] Fig.14 This is a diagram for explaining the structure of the aberration optical system in Embodiment 1.

[0026] Fig.15 This is a diagram for explaining changes in the relationship between lateral aberration and divergence angle when the aspherical surface shape of the aberration lens is changed in Embodiment 1.

[0027] Fig.16 This is a diagram for explaining changes in the beam profile when the aspherical surface shape of the aberration lens is changed in Embodiment 1.

[0028] Fig.17 This is a diagram showing an example of the relationship between the aspheric coefficient and the lateral aberration in the first embodiment.

[0029] Fig.18 It means about having Fig.17 A diagram showing an example of the relationship between the characteristics of aberrations and lens parameters.

[0030] Fig.19 ΔY is an aberration generated by the processing optical system when a convex aberration lens is used in Embodiment 1. O A diagram showing an example of the relationship with the aspherical coefficient A4.

[0031] Fig. 20 ΔY is an aberration generated by the processing optical system when a convex aberration lens is used in Embodiment 1. O A diagram showing an example of the relationship between θ and the movement amount d of the aberration lens.

[0032] Fig.21 This is a diagram showing an example of the relationship between the aspheric coefficient A4 and the movement amount d of the aberration lens when a convex aberration lens is used in Embodiment 1.

[0033] Fig. 22ΔY is an aberration generated by the processing optical system when a concave aberration lens is used in Embodiment 1. O A diagram showing an example of the relationship with the aspherical coefficient A4.

[0034] Fig.23 ΔY is an aberration generated by the processing optical system when a concave aberration lens is used in Embodiment 1. O A diagram showing an example of the relationship between θ and the movement amount d of the aberration lens.

[0035] Fig.24 This is a diagram showing an example of the relationship between the aspheric coefficient A4 and the movement amount d of the aberration lens when a concave aberration lens is used in Embodiment 1.

[0036] Fig.25 It means about having Figures 19 to 21 The relationship shown is the aberration characteristics of the lens and has as Figure 22 to Figure 24 A diagram showing an example of the relationship between the characteristics of aberrations and lens parameters.

[0037] Fig.26 This is a diagram showing the structure of a laser processing device involved in the first example of embodiment 2.

[0038] Fig. 27 This is a diagram for explaining the structure of the aberration optical system in Embodiment 2.

[0039] Fig.28 This is a diagram showing the structure of a laser processing device according to a second example of the second embodiment.

[0040] Fig.29 This is a diagram showing the structure of a laser processing device according to a third example of the second embodiment.

[0041] Fig.30 This is a diagram showing the structure of a laser processing device involved in the first example of embodiment 3.

[0042] Fig.31 This is a diagram showing the structure of a laser processing device according to a second example of the third embodiment.

[0043] Fig.32 This is a diagram showing a configuration example of a control circuit according to the third embodiment.

[0044] Fig.33 This is a diagram showing a configuration example of a dedicated hardware circuit according to the third embodiment. DETAILED DESCRIPTION

[0045] Hereinafter, a laser processing head, a laser processing device, and a method for manufacturing a metal product according to the embodiment will be described in detail with reference to the drawings.

[0046] Implementation method 1.

[0047] Before describing the laser processing apparatus according to the first embodiment, the definition of the lateral aberration in the first embodiment will be described. It is assumed that the definition of the lateral aberration described here is common to the first embodiment and the second and third embodiments described later.

[0048] Figure 1 1 is a first diagram for explaining the definition of lateral aberration in Embodiment 1. Figure 1 In FIG. 1 , it is schematically shown that light emitted from a light source is focused by a collimating optical system and a focusing optical system. Figure 1 In , the light source is a point light source 111. Figure 1 (A) and (B) show the difference in the behavior of light rays when light rays with different divergence angles are emitted from the point light source 111. Figure 1 (A) shows the case where light with a divergence angle θ1 is emitted from a point light source 111. Figure 1 (B) shows a case where light having a divergence angle θ2 is emitted from a point light source 111. It is assumed that θ1>θ2>0. The divergence angle is represented by a half angle.

[0049] In the following description, the collimating optical system is assumed to be a collimating lens 112 which is a single lens. The focusing optical system is assumed to be a focusing lens 113 which is a single lens. The collimating lens 112 is assumed to be a lens which does not generate aberration. The collimating lens 112 may also be a lens which generates aberration which is so small as to be negligible. The focusing lens 113 is assumed to be a spherical lens which generates spherical aberration. The collimating lens 112 is arranged at a distance f from the point light source 11. c The distance f c is the focal length of the collimating lens 112. Distance f f is the focal length of the focusing lens 113. Let the z direction be the direction of the central axis of the collimating optical system and the focusing optical system. The optical axis of the laser overlaps with the central axis. The r direction is one of the directions perpendicular to the central axis, and let the r direction be the radial direction of the collimating lens 112 and the focusing lens 113.

[0050] Assume that light 121 is a light emitted from point light source 111 at divergence angle θ1. Assume that light 122 is a light emitted from point light source 111 at divergence angle θ2. Light 121 passing through collimating lens 112 is parallelized to become a light whose height from the optical axis is h1. Light 122 passing through collimating lens 112 is parallelized to become a light whose height from the optical axis is h2. i =f c tanθ i (i=1,2) holds. i Sufficiently small and tanθi ≈θ i When the approximation of i ≈f c θ i In the following description, the height of a light ray from the optical axis is referred to as the light ray height.

[0051] The parallelized light rays 121 and 122 are focused by the focusing lens 113. In the case of the divergence angle θ1, the parallelized light rays 121 are focused by the focusing lens 113, and a lateral aberration ΔY1 is generated at the paraxial focus 117. In the case of the divergence angle θ2, the parallelized light rays 122 are focused by the focusing lens 113, and a lateral aberration ΔY2 is generated at the paraxial focus 117.

[0052] Figure 2 2 is a second diagram for explaining the definition of lateral aberration in Embodiment 1. Figure 2 , a graph showing the relationship between the lateral aberration ΔY and the light ray height h is shown. The lateral aberration ΔY caused by the spherical aberration i With the light height h i Proportional to the cube of (ΔY i ∝h i 3 ). i ≈θ i If the approximation of h i ≈f c θ i , lateral aberration ΔY i With divergence angle θ i Proportional to the cube of (ΔY i ∝θ i 3 ).

[0053] exist Figure 1 In order to make the divergence angle θ i The height of the light h at the positive i A positive r direction is defined as the radial direction. Figure 1 ΔY shown i Since it is generated in the negative direction of r, it is a negative lateral aberration. According to this result, when θ1>θ2, ΔY1<ΔY2, and

[0054] |ΔY1|>|ΔY2| holds. Hereinafter, the lateral aberration generated in the negative direction of r is defined as negative lateral aberration, and the lateral aberration generated in the positive direction of r is defined as positive lateral aberration.

[0055] In addition, Figure 1In order to simply explain the relationship between the lateral aberration and the divergence angle, the light 121 emitted from the point light source 111 at the divergence angle θ1 and the light 122 emitted from the point light source 111 at the divergence angle θ2 are used in the description. In the following embodiments, the lateral aberration of the laser is defined for the light emitted at an angle equivalent to the divergence angle in the laser emitted from the emission portion such as the emission end of the optical fiber, and the lateral aberration defined for the light is referred to as the lateral aberration in the same manner as the case of the point light source 111.

[0056] Next, the configuration of the laser processing apparatus according to Embodiment 1 will be described. In Embodiment 1, three configuration examples will be described. Figure 3 This is a diagram showing the structure of a laser processing device 21 according to a first example of Embodiment 1. The laser processing device 21 processes an object by partially melting the object by irradiating it with laser light. The laser processing device 21 performs laser processing such as cutting, welding, or heat treatment.

[0057] The laser processing device 21 includes a laser oscillator 141 as a light source, an optical fiber 142 as a transmission path of a laser beam 144, and a laser processing head 116. The laser processing head 116 includes a collimating lens 112 and a focusing lens 113 for propagating the laser beam. Hereinafter, the optical system including the collimating lens 112 and the focusing lens 113 is referred to as a processing optical system 114.

[0058] The laser oscillator 141 is a laser that outputs near-infrared laser light 144, such as a fiber laser, a YAG laser, or a DDL. The YAG laser may also be a disk laser using a disk-shaped medium. The laser oscillator 141 has, for example, a kilowatt-class output capable of processing metals, etc. The laser output of the laser oscillator 141 is typically 1 kW, and is preferably 4 kW or more when processing thick metals, etc. The laser output of the laser oscillator 141 may also be 10 kW or more.

[0059] The laser beam 144 output from the laser oscillator 141 propagates in the optical fiber 142. The optical fiber 142 is, for example, an optical fiber capable of propagating the kilowatt-class laser beam 144. The intensity distribution of the light beam at the output end of the optical fiber 142 is, for example, a top hat shape. The core diameter of the optical fiber 142 is For example, it is 50 μm, 100 μm, 150 μm, 200 μm, or 300 μm. Profile 118 is the beam profile of laser light 144 at the emission end of optical fiber 142. Profile 119 is the beam profile of laser light 144 incident on object 143.

[0060] The laser 144 emitted from the optical fiber 142 diverges. Based on the divergence angle θ of the laser 144 and the beam waist radius ω0, the beam parameter product (Beam Parameter Products: BPP) is expressed as ω0θ. When the beam profile at the emission end of the optical fiber 142 is a top hat shape, the beam waist radius ω0 is Therefore, it can be expressed as

[0061] The BPP of the laser light 144 output from the optical fiber 142 may differ depending on the type of the laser oscillator 141. In addition, even if the laser oscillator 141 is of the same type, the BPP of the laser light 144 output from the optical fiber 142 may differ depending on the individual laser oscillator 141. When the core diameter is 100 μm, the BPP is, for example, about 2.5 mm·mrad to 5.5 mm·mrad. When the diameter is 200 μm, the BPP is, for example, about 5.0 mm·mrad to 11.0 mm·mrad. These BPP ranges correspond to the divergence angle θ of 50 mrad to 110 mrad.

[0062] Figure 3 The processing optical system 114 shown generates aberrations. The collimating lens 112 is arranged at a distance f from the output end of the optical fiber 142. c The laser beam 144 that has passed through the collimating lens 112 passes through the focusing lens 113 and is focused on the processing object 143 .

[0063] The focal length of the collimating lens 112 is the distance f c and the focal length of the focusing lens 113, i.e., the distance f f For example, they are about 50 mm to 600 mm respectively. c and distance f f Converted to the reciprocal of focal length, i.e., optical power, the optical power of the collimating lens 112 and the optical power of the focusing lens 113 are respectively about 1.67D to 20D. D is the unit of optical power, i.e., diopter, which is expressed in SI basic units as m -1 For example, at a distance f c is 200mm, and the distance f f When the distance f is 200 mm, the processing optical system 114 is configured with an optical magnification of 1. c is 200mm, and the distance f f When the distance is 400 mm, the processing optical system 114 is configured with an optical magnification of 2. Furthermore, by changing the combination of the focal length of the collimating lens 112 and the focal length of the condensing lens 113, the processing optical system 114 with other optical magnifications can be configured.

[0064] In addition, the collimating lens 112 and the focusing lens 113 are not limited to single lenses, but may include more than two lenses. In this case, the focal length of the collimating lens 112 is the combined focal length of the combination of more than two lenses. The focal length of the focusing lens 113 is the combined focal length of the combination of more than two lenses.

[0065] The object 143 to be processed is, for example, a metal product made of a metal such as mild steel, copper, aluminum, stainless steel or galvanized steel. The metal product may be a metal component or a metal plate. The laser processing device 21 for laser welding may irradiate the laser 144 to each of the first metal product and the second metal product, and perform laser welding through existing welded joints such as butt welding, fillet welding or lap welding. The first metal product and the second metal product are the objects 143 to be processed in laser welding, respectively. The laser processing device 21 can manufacture a third metal product in which the first metal product and the second metal product are joined by laser welding the first metal product and the second metal product.

[0066] Next, the relationship between the laser processing state and aberration in the first embodiment will be described. Figure 4 This is the first diagram for explaining the relationship between the laser processing state and aberration in the first embodiment.

[0067] Figure 5 This is the second diagram for explaining the relationship between the laser processing situation and aberration in the first embodiment. Figure 6 The third diagram is used to explain the relationship between the laser processing situation and aberration in the first embodiment.

[0068] exist Figures 4 to 6 , a state where the object 143 is processed by irradiating the object 143 with a laser beam 144 is schematically shown. Figure 4 , an example of focusing the laser light 144 using the processing optical system 114 that does not generate aberrations is shown. The processing optical system 114 may also be an optical system that generates aberrations that are small enough to be ignored. Figure 5 and Figure 6 , an example of focusing the laser light 144 using the processing optical system 114 that generates aberrations is shown. Figure 6 In the figure, it is shown that Figure 5 The state shown is smaller than the state where the absolute value of the lateral aberration is smaller. Figures 4 to 6 The processing optical system 114 is omitted in the figure. The x direction and the y direction are assumed to be mutually perpendicular directions and are also perpendicular to the z direction. The advancing direction 120 is assumed to be the advancing direction of the processing in the processing object 143. The advancing direction 120 can also be said to be the scanning direction of the laser 144 in the processing object 143. Figures 4 to 6 , the forward direction 120 is the x direction.

[0069] like Figure 4 As shown, when the processing optical system 114 that does not generate aberration is used, the profile 119 at the irradiation position of the laser light 144 in the processing object 143 is obtained by multiplying the profile 118 at the emission end of the optical fiber 142 by an optical magnification M=f f / f c The enlarged top-hat-shaped outline 145.

[0070] Figure 7 Yes means Figure 4 A diagram of the beam shape of laser light 144 is shown. Figure 7 The beam shape shown is the beam shape of the laser 144 incident on the processing object 143, and is the beam shape on the xy plane. The beam shape of the laser 144 incident on the processing object 143 is as follows: Figure 7 A circle is shown.

[0071] The intensity I of the laser 144 having the top-hat-shaped profile 145 is, for example, 200 kW / cm 2 In the above, the object 143 is melted by the irradiated laser light 144, and a keyhole 147 is formed in the object 143. At this time, the front wall 148 and the rear wall 149 of the keyhole 147 are respectively in a state nearly perpendicular to the reference plane 154 from the bottom 152 of the keyhole 147 to the opening 155 in the surface 153 of the object 143. The front wall 148 is a front wall in the keyhole 147 in the advancing direction 120. The rear wall 149 is a rear wall in the keyhole 147 in the advancing direction 120. The surface 153 is a surface of the object 143 on which the laser light 144 is incident. The reference plane 154 is a surface perpendicular to the central axis of the processing optical system 114, for example, a surface on which the object 143 is placed. It is assumed that the surface 153 is parallel to the reference plane 154 when the object 143 is placed on the reference plane 154.

[0072] exist Figure 4 In the embodiment, the molten metal flow 150 as the flow of the molten metal 151 rises at a relatively high speed along the rear wall 149 from the bottom 152 to the opening 155. A part of the molten metal 151 is scattered as splashes 146 by the molten metal flow 150. Figure 4 When the processing optical system 114 that does not generate aberration is used as shown, there is a possibility that the processing may become unstable due to the generation of spatter 146 .

[0073] In such Figure 5When the processing optical system 114 that generates aberrations is used as shown, the contour 119 at the irradiation position of the laser light 144 in the processing object 143 is a witch's hat-shaped contour 165 having a main beam 160 at the center and peripheral beams 161 surrounding the main beam 160 .

[0074] Figure 8 Yes means Figure 5 A diagram of the beam shape of laser light 144 is shown. Figure 8 The beam shape shown is the beam shape of the laser beam 144 incident on the processing object 143, and is the beam shape on the xy plane. The beam shape of the laser beam 144 incident on the processing object 143 is a concentric circle of the main beam 160 and the circle of the peripheral beam 161. The peripheral beam width 166 is the width between the circle of the peripheral beam 161 and the circle of the main beam 160.

[0075] exist Figure 5 In the case shown, the absolute value of the lateral aberration generated at the paraxial focus 117 of the laser light 144 passing through the processing optical system 114 is, for example, greater than 0.2 mm. In the following description, the paraxial focus 117 of the laser light 144 passing through the processing optical system 114 is simply referred to as the paraxial focus 117 of the processing optical system 114. The paraxial focus 117 of the laser light 144 passing through the laser processing head 116 is simply referred to as the paraxial focus 117 of the laser processing head 116.

[0076] The intensity I of the laser light 144 with the witch hat-shaped profile 165 is, for example, 200 kW / cm 2 When the main beam 160 is irradiated, the object 143 is melted, and a keyhole 147 is formed in the object 143. In this case, the intensity I of the peripheral beam 161 is, for example, 50 kW / cm 2 Up to 200kW / cm 2 In addition, the intensity I of the peripheral light beam 161 may be an intensity at which the keyhole 147 is not formed.

[0077] The molten metal 151 evaporates from the surface of the molten metal 151 by the irradiation of the peripheral light beam 161, thereby generating metal vapor 163. The evaporation reaction force 162 generated by the generation of the metal vapor 163 acts from the surface of the molten metal 151 toward the inside of the processing object 143 in the opening 155 of the keyhole 147. Due to the action of the evaporation reaction force 162, the molten metal flow 150 rising along the rear wall 149 in the rear in the advancing direction 120 changes from a direction perpendicular to the surface 153 to a direction parallel to the surface 153. Due to such a change in the molten metal flow 150, the opening 155 expands in a trumpet shape. Due to the trumpet-shaped expansion of the opening 155, the molten metal flow 150 moves from the surface 153 toward the inside of the processing object 143. Due to the molten metal flow 150, the keyhole 147 is stabilized, and the situation where a part of the molten metal 151 becomes spatter 146 and scatters is reduced.

[0078] In addition, the opening 155 is expanded in a trumpet shape, so that the metal vapor 163 in the keyhole 147 can easily escape from the front wall 148 to the opening 155. The keyhole 147 is stabilized by the easy escape of the metal vapor 163, and the situation where a part of the molten metal 151 becomes splash 146 and scatters is reduced. Figure 5 In the case of the machining shown, stable machining can be performed by stabilizing the keyhole 147 and reducing the spatter 146 .

[0079] exist Figure 6 In the case shown, the processing optical system 114 that generates aberration is used, but the absolute value of the generated lateral aberration is smaller than that of Figure 5 The outline 119 at the irradiation position of the laser beam 144 in the object 143 is a witch's hat-shaped outline 167 having a main beam 160 at the center and peripheral beams 161 surrounding the main beam 160 .

[0080] Fig. 9 Yes means Figure 6 A diagram of the beam shape of laser light 144 is shown. Fig. 9 The beam shape shown is the beam shape of the laser beam 144 incident on the object 143 and is the beam shape on the xy plane. The beam shape of the laser beam 144 incident on the object 143 is a concentric circle of the main beam 160 and the peripheral beam 161 . Fig. 9 The peripheral beam width shown is 166 Figure 8 The peripheral beam width 166 is shown to be small.

[0081] exist Figure 6 In the case shown, the absolute value of the lateral aberration generated by the laser light 144 passing through the processing optical system 114 at the paraxial focus 117 is, for example, less than 0.2 mm. Figure 6 The witch hat-shaped outline 167 of the laser 144 is shown with Figure 5 The situation shown is smaller than the peripheral beam width 166, so the opening 155 cannot be expanded into a trumpet shape. Figure 6 In the case shown in FIG. 1 , although the processing optical system 114 generates aberrations to form a peripheral beam 161, Figure 5 Compared with the situation shown in FIG. 1 , the scattering of the splash 146 cannot be reduced. Figure 6 The absolute value of the lateral aberration produced as shown in the figure is compared with Figure 5 In the case where the amount of spatter 146 is small, the machining may become unstable due to the generation of spatter 146 .

[0082] As reference Figures 4 to 6 As described above, if the amount of aberration generated by the processing optical system 114 changes, the beam shape of the laser 144 at the irradiation position changes, and the stability of the processing may change. Therefore, if a constant amount of aberration can be generated, the beam shape is stable and stable processing can be achieved.

[0083] As described above, the divergence angle of the laser light 144 at the emission end of the optical fiber 142 is, for example, 50 mrad to 100 mrad. In addition, the divergence angle of the laser light 144 may differ depending on the type of the laser oscillator 141, and may differ from one laser oscillator 141 to another even if the laser oscillator 141 is of the same type. Figure 1 As shown in FIG. 1 , the lateral aberration caused by the spherical aberration varies according to the divergence angle of the laser light 144. Therefore, even if the same processing optical system 114 is used, the lateral aberration may vary depending on the type of laser oscillator 141 or the individual laser oscillator 141, thereby causing the beam shape at the irradiation position to vary. Due to such a change in the beam shape, the processing state of the laser processing device 21 may vary, and the processing quality of the laser processing device 21 may also vary.

[0084] Fig.10 FIG. 2 is a diagram showing the structure of a laser processing device 31 according to a second example of the first embodiment. The laser processing device 31 includes Figure 3 The laser processing device 21 shown in the figure has a similar structure and further includes an aberration optical system that generates aberrations. In the second example, the aberration optical system is an aberration lens 171 that is a single lens. The aberration lens 171 is a convex lens having a convex surface that is an aspherical surface.

[0085] The laser processing head 116 includes an aberration lens 171, a collimating lens 112, and a focusing lens 113. In addition, the laser processing head 116 includes a movable mechanism 172 for moving the aberration lens 171 in the direction of the optical axis. The laser processing device 31 includes a control device for controlling the movable mechanism 172. In the second example, the processing optical system 114 is an optical system that does not generate aberration. The processing optical system 114 may also be an optical system that generates aberrations that are small enough to be ignored. In addition, in Fig.10 The illustration of the processing object 143 and the control device is omitted.

[0086] The aberration lens 171 is disposed on the optical path of the laser light 144 between the emission end of the optical fiber 142 and the collimating lens 112. The aberration lens 171 is disposed at a position within a range where the laser light 144 irradiated toward the object 143 extends in the propagation direction of the laser light 144, that is, in the direction approaching the object 143. The aberration lens 171 generates lateral aberration.

[0087] exist Fig.10 (A) and (B) show the difference in the behavior of the laser light 144 when the laser light 144 with different divergence angles is emitted from the emission end of the optical fiber 142. Fig.10 (B) shows the divergence angle of the laser 144 emitted from the output end of the optical fiber 142 compared to Fig.10 The case shown in (A) is a case where the laser processing device 31 is small. Fig.10 In the state shown in (B) Fig.10 Compared with the state shown in (A), the aberration lens 171 is moved by an amount d in a direction approaching the processing object 143.

[0088] The laser processing device 31 can maintain the lateral aberration generated at the paraxial focus 117 of the laser processing head 116 at a constant lateral aberration ΔY2 by changing the position of the aberration lens 171 in the z direction when the divergence angle of the laser 144 changes. The laser processing device 31 reduces the change in the beam shape at the irradiation position between each type of laser oscillator 141 or each individual laser oscillator 141 by maintaining the lateral aberration. Thus, the laser processing device 31 can achieve stable processing.

[0089] Fig.11 1 is a diagram for explaining the change in lateral aberration caused by moving the aberration lens 171 in the second example of the first embodiment. Fig.11 In FIG. 1 , a graph showing the relationship between the lateral aberration ΔY and the divergence angle θ is shown. Fig.11 In the figure, the dashed line 190 indicates Fig.10 The relationship between the lateral aberration and the divergence angle in the case shown in (A). Fig.11In the figure, the solid line 191 indicates Fig.10 The relationship between the lateral aberration and the divergence angle in the case shown in (B).

[0090] Located in Fig.10 In the case shown in (A), the divergence angle θ of the laser light 144 emitted from the emission end of the optical fiber 142 is θ1. Fig.10 In the case shown in (B), the divergence angle θ of the laser 144 emitted from the emission end of the optical fiber 142 is θ2. Here, θ1>θ2. Fig.10 The situation shown in (A) and Fig.10 In the case shown in (B), the lateral aberration ΔY generated in these two cases is ΔY2.

[0091] As reference Figure 2 As described above, the lateral aberration ΔY is proportional to the cube of the divergence angle θ. Let α1 be the proportionality constant, ΔY=α1θ 3 Established. That is, the dependence of the lateral aberration ΔY generated by the aberration lens 171 on the divergence angle θ is the same as that of the spherical aberration. By moving the aberration lens 171 in the direction of the optical axis, the proportional constant α1 changes. By changing the proportional constant α1, even if the divergence angle θ changes to either θ1 or θ2, the lateral aberration ΔY is the same ΔY2. That is, even if the divergence angle θ changes from θ1 to θ2, the lateral aberration ΔY remains ΔY2.

[0092] exist Fig.10 In the laser processing head 116 shown, an aberration lens 171 is arranged on the optical path of the laser light 144 emitted from the emission end of the optical fiber 142. The collimator lens 112 is arranged on the optical path of the laser light 144 passing through the aberration lens 171. The condenser lens 113 is arranged on the optical path of the laser light 144 passing through the collimator lens 112.

[0093] The aberration lens 171 is not limited to being arranged on the optical path where the laser light 144 diverges between the emission end of the optical fiber 142 and the collimating lens 112. The aberration lens 171 may also be arranged on the optical path where the laser light 144 is focused between the focusing lens 113 and the object 143. In this case, the collimating lens 112 is arranged on the optical path where the laser light 144 emitted from the emission end of the optical fiber 142 diverges. The focusing lens 113 is arranged on the optical path of the laser light 144 that has passed through the collimating lens 112. The aberration lens 171 is arranged on the optical path of the laser light 144 that has passed through the focusing lens 113.

[0094] The laser processing head 116 can change the lateral aberration at the paraxial focus 117 of the laser processing head 116 by moving the aberration lens 171 along the optical axis on the optical path of the diverging or focused laser light 144. Here, divergence means that the beam diameter of the laser light 144 expands as it propagates. Focusing means that the beam diameter of the laser light 144 decreases as it propagates.

[0095] Through Fig.10 As shown in the figure, the aberration lens 171 is arranged on the optical path of the diverging laser light 144, and the position of the aberration lens 171 is far from the irradiation position of the laser light 144. Since the position of the aberration lens 171 is far from the irradiation position of the laser light 144, when the spatter 146 is scattered from the processing object 143, the spatter 146 is prevented from being attached to the aberration lens 171. Thus, the laser processing device 31 can prevent the aberration lens 171 from being damaged due to the laser light 144 passing through the aberration lens 171 to which the spatter 146 is attached.

[0096] The laser processing device 31 may also include a protective plate for protecting the processing optical system 114 and the aberration lens 171 from damage caused by the adhesion of the spatter 146. The protective plate is arranged on the optical path of the laser light 144 between the condenser lens 113 and the processing object 143. The protective plate is made of a material transparent to the laser light 144 and allows the laser light 144 to pass through. In addition, the protective plate may be arranged on the optical path of the laser light 144 between the emission end of the optical fiber 142 and the aberration lens 171 to protect the processing optical system 114 and the aberration lens 171.

[0097] The aberration lens 171 is, for example, a plano-convex aspheric lens having a first surface 181 which is an aspheric and convex surface and a second surface 182 which is a flat surface. Fig.10 In the laser processing device 31 shown, the first surface 181 is the incident surface of the laser 144, and the second surface 182 is the exit surface of the laser 144. Alternatively, the first surface 181 is the exit surface of the laser 144, and the second surface 182 is the incident surface of the laser 144.

[0098] Generally, the shape of an aspherical surface is defined by the vector height amount, which is the amount of cutting in the direction of the central axis of the lens. The vector height amount z(r) is expressed by the following equation (1).

[0099] [Number 1]

[0100]

[0101] Let C0 be the curvature C on the central axis, k be the cone constant, A j is the aspheric coefficient. Let j be an even number greater than 4. The curvature C is defined by the following formula (2).

[0102] [Number 2]

[0103]

[0104] Where z'(r) = dz / dr and z"(r) = d 2 z / dr 2 holds. C0 is the curvature C when r=0. When the first surface 181 is an aspheric surface having a C0 value other than zero and the second surface 182 is a plane, as the aberration lens 171 moves in the direction of the optical axis, the position of the paraxial focus 117 of the laser processing head 116 also moves in the direction of the optical axis. Therefore, the first surface 181 of the aberration lens 171 may also be an aspheric surface with C0=0. Based on equation (1), the vector height z(r) when C0=0 is expressed by the following equation (3).

[0105] [Number 3]

[0106] z(r)=A4r 4 +A6r 6 +A8r 8 ……(3)

[0107] If the first surface 181 is set to an aspherical surface of the shape shown in the formula (3) with C0=0, and the second surface 182 is set to a plane, the position of the paraxial focus 117 of the laser processing head 116 does not move even if the aberration lens 171 is moved in the direction of the optical axis. The laser processing device 31 can keep the irradiation position of the laser 144 constant by not moving the position of the paraxial focus 117 of the laser processing head 116. In addition, for example, when the aspherical shape of the sixth order or more is set to zero in the formula (3) and the terms up to the term A4 which is the fourth order term is used on the left side of the formula (3), the value of the aspherical coefficient A4 in the aberration lens 171 is a positive value.

[0108] Fig.12 1 is a diagram showing the structure of a laser processing device 41 according to a third example of Embodiment 1. The laser processing head 116 includes an aberration lens 173, a collimating lens 112, and a focusing lens 113. In addition, the laser processing head 116 includes a movable mechanism 172 for moving the aberration lens 173 in the direction of the optical axis. The laser processing device 41 includes a control device for controlling the movable mechanism 172. Fig.12 The illustration of the processing object 143 and the control device is omitted.

[0109] The laser processing device 41 is provided with an aberration lens 173 instead of the aberration lens 171, which is different from Fig.10The laser processing device 31 shown. Except for this point, the laser processing device 41 is the same as the laser processing device 31. In the third example, the aberration optical system is an aberration lens 173 as a single lens. The aberration lens 173 is a concave lens having a concave surface as an aspheric surface. For example, in the formula (3), the aspheric surface shape of the sixth order or more is set to zero, and the terms up to the term A4 as the fourth order term are used on the left side of the formula (3), the value of A4 in the aberration lens 173 is a negative value.

[0110] exist Fig.12 (A) and (B) show the difference in the behavior of the laser light 144 when the laser light 144 with different divergence angles is emitted from the emission end of the optical fiber 142. Fig.12 (B) shows the divergence angle of the laser 144 emitted from the output end of the optical fiber 142 compared to Fig.12 The case shown in (A) is a case where the laser processing device 41 is small. Fig.12 In the state shown in (B) Fig.12 In the state shown in (A), the aberration lens 173 has moved by an amount d in a direction away from the object 143.

[0111] The laser processing device 41 can maintain the lateral aberration generated at the paraxial focus 117 of the laser processing head 116 at a constant lateral aberration ΔY'2 by changing the position of the aberration lens 173 in the z direction when the divergence angle of the laser 144 changes. The laser processing device 41 reduces the change in the beam shape at the irradiation position between each type of laser oscillator 141 or each individual laser oscillator 141 by maintaining the lateral aberration. Thus, the laser processing device 41 can achieve stable processing.

[0112] also, Fig.10 The laser processing device 31 of the second example shown moves the aberration lens 171 toward the emission end of the optical fiber 142 when the divergence angle increases, and moves the aberration lens 171 toward the collimator lens 112 when the divergence angle decreases. Fig.12 The laser processing device 41 of the third example shown moves the aberration lens 173 toward the collimating lens 112 when the divergence angle increases, and moves the aberration lens 173 toward the emission end of the optical fiber 142 when the divergence angle decreases. Thus, the direction in which the aberration lens 173 is moved in the third example is opposite to the direction in which the aberration lens 171 is moved in the second example.

[0113] Fig.13 1 is a diagram for explaining the change in lateral aberration caused by moving the aberration lens 173 in the third example of the first embodiment. Fig.13 In FIG. 1 , a graph showing the relationship between the lateral aberration ΔY and the divergence angle θ is shown. Fig.13 In the example, the dashed line 192 indicates Fig.12 The relationship between the lateral aberration and the divergence angle in the case shown in (A). Fig.13 In the figure, the solid line 193 indicates Fig.12 The relationship between the lateral aberration and the divergence angle in the case shown in (B).

[0114] Located in Fig.12 In the case shown in (A), the divergence angle θ of the laser light 144 emitted from the emission end of the optical fiber 142 is θ1. Fig.12 In the case shown in (B), the divergence angle θ of the laser 144 emitted from the emission end of the optical fiber 142 is θ2. Here, θ1>θ2. Fig.12 The situation shown in (A) and Fig.12 In the case shown in (B), the lateral aberration ΔY generated in these two cases is ΔY'2. Even if the divergence angle θ changes from θ1 to θ2, the lateral aberration ΔY is maintained at ΔY'2 by moving the aberration lens 173 in the direction of the optical axis.

[0115] exist Fig.12 In the laser processing head 116 shown, an aberration lens 173 is arranged on the optical path of the laser light 144 emitted from the emission end of the optical fiber 142. In addition, the aberration lens 173 may be arranged on the optical path where the laser light 144 is condensed between the condensing lens 113 and the processing object 143. By making the position of the aberration lens 173 away from the irradiation position of the laser light 144, the spatter 146 is prevented from adhering to the aberration lens 173. Thus, the laser processing device 41 can prevent the aberration lens 173 from being damaged due to the laser light 144 passing through the aberration lens 173 to which the spatter 146 is attached. In addition, the laser processing device 41 may also be provided with a protective plate for protecting the processing optical system 114 and the aberration lens 171 from damage caused by the attachment of the spatter 146. In the laser processing device 41, a protective plate may be arranged on the optical path of the laser light 144 between the emission end of the optical fiber 142 and the aberration lens 171.

[0116] The aberration lens 173 is, for example, a plano-concave aspheric lens having a first surface 183 which is an aspheric and concave surface and a second surface 184 which is a flat surface. Fig.12 In the laser processing device 41 shown, the first surface 183 is the incident surface of the laser 144, and the second surface 184 is the exit surface of the laser 144. Alternatively, the first surface 183 is the exit surface of the laser 144, and the second surface 184 is the incident surface of the laser 144.

[0117] Fig.14 1 is a diagram for explaining the structure of the aberration optical system in Embodiment 1. Fig.14In (A) and (B), the shapes of the aberration lenses 171 and 173 as the aberration optical system, the curvature C of the aspheric surfaces of the aberration lenses 171 and 173, and the focal positions z of the aberration lenses 171 and 173 are shown. f For example. Fig.14 In FIG. 1 , the shape of the aberration lens indicates the shape of the cross section including the r direction and the z direction. Regarding the curvature C, a graph indicating the relationship between the position in the r direction and the curvature C is shown. Regarding the focal position z f , showing the r direction position and the focal position z f In addition, the position in the r direction is represented by the r coordinate based on the position of the central axis. In addition, the r coordinate is simply referred to as "r".

[0118] Set the focus position z f When a light ray advancing in the direction of the central axis enters the aberration lens arranged at the position z=0, the light ray bent by the aberration lens intersects the central axis. For example, when a thin lens with a focal length of f as a convex lens is arranged at the position z=0, z f =f. When a thin lens with a focal length of -f, which is a concave lens, is arranged at the position z=0, z f = -f. In the lens that produces aberration, the focal position z f The aberration varies depending on the distance between the light rays parallel to the central axis and the central axis. The focal position z of the lens that produces the aberration f The distance between the light and the central axis varies according to the direction of the central axis. Fig.14 In the figure, about the focal position z f The focal position z is shown when the incident position of the light in the direction of the central axis is changed in the r direction. f Examples of changes.

[0119] exist Fig.14 In (A), it is shown about Fig.10 The shape, curvature C, and focal position z of the aberration lens 171 are shown in FIG. f For example. Fig.14 In (B), it is shown about Fig.12 The shape, curvature C and focal position z of the aberration lens 173 shown in FIG. f For example. Fig.14 In (C), the shape, curvature C, and focal position z of the plano-convex spherical lens 180 are shown for comparison with the aberration lens 171. fExample. The curvature C of the plano-convex spherical lens 180 is constant and independent of r. In contrast, the curvature C of the aberration lens 171 increases monotonically as the absolute value of r increases. The curvature C of the aberration lens 173 decreases monotonically as the absolute value of r increases. That is, in the aberration lens 171, the curvature C increases monotonically as it moves away from the central axis in the radial direction. In the aberration lens 173, the curvature C decreases monotonically as it moves away from the central axis in the radial direction.

[0120] The focal position z of the aberration lens 171 f As the absolute value of r decreases, it increases. In the aberration lens 171, the focal position z of the light on the central axis is f is positive infinity. That is, the aberration lens 171 has no optical power for the light on the central axis. The focal position z of the aberration lens 173 is f As the absolute value of r decreases, it decreases. In the aberration lens 173, the focal position z of the light on the central axis is f is negative infinity. That is, the aberration lens 173 has no optical power for the light on the central axis. In addition, the so-called "no optical power for the light on the central axis" includes the case where the optical power for the light on the central axis is so small that it can be ignored.

[0121] The above contents can be summarized as follows. In each of the aberration lenses 171 and 173, as the absolute value |r| of r increases, the focal position z f The absolute value of |z f |Get smaller. |z f | is the distance between the aberration lens 171 and the focal point, or the distance between the aberration lens 173 and the focal point. |r| represents the distance between the central axis and the light parallel to the central axis. In other words, the aberration lenses 171 and 173 have the following focusing characteristics: when the light parallel to the central axis is incident on the aberration lenses 171 and 173, the farther the position of the light is from the central axis, the shorter the distance between the aberration lenses 171 and 173 and the focal point. Thus, the aberration lenses 171 and 173 generate aberrations.

[0122] In the plano-convex spherical lens 180, as |r| increases, |z f | becomes smaller. However, the difference between the plano-convex spherical lens 180 and the aberration lens 171 is that the focal position z of the light on the central axis is f The focal position z of the plano-convex spherical lens 180 is f For example, it is a quadratic function of r.

[0123] When the aberration lenses 171 and 173 are actually manufactured, the focal length on the central axis cannot be completely zero. Therefore, the aberration lenses 171 and 173 may also have focal length on the central axis within a range in which the position of the paraxial focus 117 of the laser processing head 116 does not change significantly. The absolute value of the focal length on the central axis of the aberration lenses 171 and 173 is, for example, less than 1 / 10 of the focal length of the collimating lens 112. The absolute value of the focal length on the central axis of the aberration lenses 171 and 173 may also be less than 1 / 100 of the focal length of the collimating lens 112.

[0124] When the focal length f of the collimating lens 112 is c When the distance is 200 mm, the focal length of the collimating lens 112 is equivalent to 5D, so the absolute value of the focal length on the central axis of the aberration lenses 171 and 173 is, for example, 0.5D or less, which is equivalent to 1 / 10 of 5D or less. The absolute value of the focal length on the central axis of the aberration lenses 171 and 173 may also be 0.05D or less, which is equivalent to 1 / 100 of the focal length of the collimating lens 112 or less.

[0125] Thus, the positions on the central axis of the aberration lenses 171 and 173 have no optical power, or the absolute value of the optical power is less than 1 / 10 or less than 1 / 100 of the optical power of the collimating lens 112. The aberration lenses 171 and 173 can avoid a large change in the position of the paraxial focus 117 of the laser processing head 116 at the position on the central axis.

[0126] exist Fig.14 (D) shows the shape, curvature C and focal position z of the aberration lens 174. f The aberration lens 174 is different from the aberration lens 171 in that it has an aspheric surface with zero curvature in the central area 185. Except for this point, the aberration lens 174 is the same as the aberration lens 171. Fig.10 In the laser processing device 31 shown, an aberration lens 174 may be provided in place of the aberration lens 171. The aberration lens 174 is an aberration optical system provided in the laser processing head 116 and is a single lens.

[0127] In the aberration lens 174, the central region 185 is a region including a position on the central axis. The peripheral region 186 is a region surrounding the central region 185. The lens radius of the aberration lens 174 is denoted by r d , r indicating the boundary between the central region 185 and the peripheral region 186 is set to the boundary value r0. Let r0 be a positive real number. The central region 185 is an area in the range of -r0≤r≤r0 in the direction perpendicular to the central axis. The peripheral region 186 is an area in the range of -r0≤r≤r0 in the direction perpendicular to the central axis. d ≤r<-r0 or r0 <r≤r dThat is, the central region 185 is a region whose distance from the central axis is less than the boundary value r0. The peripheral region 186 is a region whose distance from the central axis exceeds the boundary value r0.

[0128] exist Fig.14 In the aberration lens 171 shown in (A), the curvature is zero at the position on the central axis, while in the aberration lens 174, the curvature is zero in the central region 185 where -r0≤r≤r0. The aberration lens 174 can be easily manufactured by setting the curvature of the central region 185 to zero, that is, by setting the central region 185 to a plane. The curvature of the peripheral region 186 increases monotonically as the absolute value of r |r| increases. That is, in the peripheral region 186, the curvature increases monotonically as it moves away from the central axis in the radial direction.

[0129] The boundary value r0 is, for example, the lens radius r d The boundary value r0 can also be a value less than 50% of the lens radius r d 40% or less, or the lens radius r d The aberration lens 174 is formed by replacing the central region of the aberration lens 171 with a central region 185 having zero curvature. The aberration lens 174 has no optical power in the central region 185 and increases |z in the peripheral region 186 as |r| increases. f | becomes smaller. In addition, the aberration lens 174 may also be Fig.14 The central area of ​​the aberration lens 173 shown in (B) is replaced by a central area 185 with zero curvature.

[0130] When the aberration lens 174 is actually manufactured, it is impossible to make the focal power in the central area 185 completely zero. Therefore, the aberration lens 174 may have the focal power in the central area 185 within a range in which the position of the paraxial focus 117 of the laser processing head 116 does not change significantly. The absolute value of the focal power in the central area 185 of the aberration lens 174 is, for example, less than 1 / 10 of the focal power of the collimating lens 112. The absolute value of the focal power in the central area 185 of the aberration lens 174 may also be less than 1 / 100 of the focal power of the collimating lens 112.

[0131] When the focal length f of the collimating lens 112 is c When the distance is 200 mm, the focal length of the collimating lens 112 is equivalent to 5D, so the absolute value of the focal length in the central area 185 of the aberration lens 174 is, for example, 0.5D or less, which is equivalent to 1 / 10 of 5D or less. The absolute value of the focal length in the central area 185 of the aberration lens 174 may also be 0.05D or less, which is equivalent to 1 / 100 of the focal length of the collimating lens 112 or less.

[0132] Thus, the central region 185 of the aberration lens 174 has no optical power, or the absolute value of the optical power is less than 1 / 10 or 1 / 100 of the optical power of the collimating lens 112. The aberration lens 174 can prevent the position of the paraxial focus 117 of the laser processing head 116 from changing significantly in the central region 185.

[0133] The peripheral region 186 in the aberration lens 174 has the following light-gathering characteristics: when a light ray parallel to the central axis is incident on the peripheral region 186, the farther the position of the light ray is from the central axis, the shorter the distance between the aberration lens 174 and the focus of the light ray is. The aberration lens 174 can generate aberrations through the peripheral region 186. In addition, the description of the aspherical surface of the aberration lens 171 is also the same as that of the peripheral region 186 in the incident surface or the exit surface of the aberration lens 174.

[0134] So far, the aberration lens 174 is configured to be formed by deforming the aberration lens 171 so as to have a central region 185 with zero curvature. The aberration lens 174 may also be formed by deforming the aberration lens 173 so as to have a central region 185 with zero curvature. In this case, the aberration lens 174 has an aspheric surface with zero curvature in the central region 185, which is different from the aberration lens 173. Except for this point, the aberration lens 174 is the same as the aberration lens 173. In addition, the description of the aspheric surface of the aberration lens 173 is also the same as the peripheral region 186 in the incident surface or the exit surface of the aberration lens 174. In the peripheral region 186, the curvature decreases monotonically as it moves away from the central axis in the radial direction.

[0135] The movable mechanism 172 is, for example, a movable table that can move in the direction of the optical axis of the laser 144. In order to control the movement of the movable table with high precision, a servo motor, a stepping motor, etc. may be mounted in the movable mechanism 172. The movable mechanism 172 is not limited to a movable table as long as it can move in the direction of the optical axis of the laser 144. The movable mechanism 172 may also be a rotary screw structure, a linear screw structure, a cam structure, etc.

[0136] The laser processing apparatus 31, 41 is not limited to moving the aberration lenses 171, 173, 174 by the movable mechanism 172. The laser processing apparatus 31, 41 may also make the lateral aberration ΔY at the paraxial focus 117 of the laser processing head 116 constant by arranging the aberration lenses 171, 173, 174 at appropriate positions on the optical axis of the laser 144 according to the divergence angle of the laser 144.

[0137] The aspheric coefficient of equation (2) is determined so that the aspheric surface of the aberration lenses 171 and 173 or the peripheral region 186 of the aberration lens 174 becomes a shape represented by equation (2) and the lateral aberration ΔY at the paraxial focus 117 of the laser processing head 116 becomes the same value at the divergence angles θ1 and θ2. Thus, the laser processing apparatus 31 and 41 can change only the dependency of the lateral aberration ΔY on the divergence angle while maintaining the position of the paraxial focus 117 of the laser processing head 116 by moving the aberration lenses 171, 173, and 174 in the direction of the optical axis. When the laser light 144 with a divergence angle θ1 is incident, the aberration lenses 171 and 174 can change the lateral aberration ΔY generated at the paraxial focus 117 of the laser processing head 116 from ΔY2 to ΔY1 by moving the aberration lenses 171 and 174 in the direction of the optical axis. When the laser beam 144 with a divergence angle θ1 is incident, the aberration lens 173 moves in the direction of the optical axis, so that the aberration lens 173 can change the lateral aberration ΔY generated at the paraxial focus 117 of the laser processing head 116 from ΔY′2 to ΔY′1.

[0138] The laser processing apparatus 31, 41 can also use the above properties to change the lateral aberration generated at the paraxial focus 117 of the laser processing head 116, for example, according to the processing object 143. For example, when processing the processing object 143 with low absorption rate in the wavelength region of the laser oscillator 141, the laser processing apparatus 31, 41 can also move the aberration lens 171, 173, 174 in the direction of the optical axis of the laser 144 to make the lateral aberration at the paraxial focus 117 of the laser processing head 116 larger. Examples of materials with low absorption rate of the laser light 144 in the near-infrared region include copper and aluminum. The laser processing apparatus 31, 41 can reduce the spatter 146 even when processing the processing object 143 with low absorption rate of the laser light 144 by increasing the lateral aberration at the paraxial focus 117 of the laser processing head 116. Thus, the laser processing apparatus 31, 41 can achieve high-quality processing.

[0139] Fig.15 1 is a diagram for explaining the change in the relationship between the lateral aberration and the divergence angle when the aspherical shape of the aberration lens 171 is changed in Embodiment 1. Fig.15 In FIG. 1 , a graph showing the relationship between the lateral aberration ΔY and the divergence angle θ is shown. For example, the aspheric coefficient A of equation (1) can be changed. j To change the aspheric shape. Fig.15 In FIG. 1 , a solid line 191 indicates a case where an aspherical shape is applied that generates a lateral aberration ΔY proportional to the cube of the divergence angle θ. That is, under the relationship indicated by the line 191, the aberration lens 171 generates the same lateral aberration as in the case of spherical aberration. Fig.15In FIG. 1 , a dotted line 194 represents an example of a case where the dependency of the lateral aberration ΔY on the divergence angle is different from that of the case of the line 191 when applying an aspherical shape. The dependency of the lateral aberration ΔY on the divergence angle represented by the line 194 is represented by the following equation (4). Let α2 be a constant and β be a positive real number.

[0140] [Number 4]

[0141]

[0142] When α2=α1 and β=3, equation (4) is ΔY=α1θ 3 . That is, the lateral aberration ΔY is proportional to the cube of the divergence angle θ. In the following, the dependence of the lateral aberration ΔY on the divergence angle is assumed to be the relationship expressed by equation (4). The so-called dependence of the lateral aberration ΔY on the divergence angle can be said to be that the lateral aberration ΔY is proportional to the βth power of the divergence angle θ. More generally, the lateral aberration ΔY is proportional to the power of the divergence angle θ. In the following, let α2 be the proportionality constant and β be the power exponent. Line 194 shows an example of the dependence of the lateral aberration ΔY on the divergence angle when the value of the power exponent β is smaller than the value of the power exponent β in the case of line 191, i.e., 3. In this way, the lateral aberration ΔY at the paraxial focus 117 of the laser processing head 116 is proportional to the power of the divergence angle θ of the laser 144.

[0143] exist Fig.15 In the figure, when the divergence angle θ is θ1, the line 191 intersects the line 194. That is, when the divergence angle θ is θ1, the lateral aberration ΔY is the same lateral aberration ΔY1. When the divergence angle θ is θ2 which is smaller than θ1, the lateral aberration ΔY3 represented by the line 194 is smaller than the lateral aberration ΔY2 represented by the line 191.

[0144] Fig.16 1 is a diagram for explaining changes in the beam profile when the aspherical shape of the aberration lens 171 is changed in Embodiment 1. Fig.16 , the beam profile of the laser 144 at the paraxial focus 117 of the laser processing head 116 is shown.

[0145] exist Fig.16 in Fig.15 The beam profile in the case of the relationship represented by line 191 is superimposed with Fig.15 The beam profile in the case of the relationship represented by line 194. Fig.16 The contour 195 indicated by the solid line is Fig.15 The beam profile in the case of the relationship represented by line 191. Fig.16 The dotted outline 196 is Fig.15195 is a beam profile when the value of the power exponent β is 3. Profile 196 is a beam profile when the value of the power exponent β is less than 3.

[0146] Each profile 195, 196 is a witch hat-shaped beam profile. Fig.16 In order to facilitate understanding of the difference between the contours 195 and 196 , the portion of the contours 195 and 196 corresponding to the peripheral light beam 161 is shown enlarged.

[0147] The major difference between the profile 195 and the profile 196 is that the intensity of the peripheral beam 161 is higher in the profile 196 than in the profile 195. As a result, in the case of the profile 196, the intensity of the peripheral beam 161 is higher than that in the case of the profile 195. Figure 8 The peripheral beam width 166 is shown to be larger. In the case of profile 196, for example, Figure 6 The opening 155 of the keyhole 147 is expanded into a larger bell-shaped shape. Therefore, the laser processing devices 31 and 41 can obtain a higher effect of reducing the spatter 146 and can achieve high-quality processing.

[0148] For the bell-shaped mouth, see Figure 6 to explain. Figure 6 The shape of the front wall 148 shown and Figure 6 The shape of the rear wall 149 shown expands as it approaches the opening 155 from the bottom 152. If the shape of the portion of the front wall 148 that expands sharply near the opening 155 and the shape of the portion of the rear wall 149 that expands sharply near the opening 155 are compared to a well-known structure, a bell-shaped mouth can be cited as an example. In addition, the expression of a bell-shaped mouth does not limit the shape of the keyhole 147. In addition, if the overall shape of the front wall 148 from the bottom 152 to the opening 155 and the overall shape of the rear wall 149 from the bottom 152 to the opening 155 are compared to a well-known structure, a trumpet or a horn having a cylindrical portion that expands more gently and an end that expands sharply compared to the cylindrical portion can be cited as an example. Therefore, if the keyhole 147 is compared to the whole, words such as trumpet-shaped or trumpet-shaped can also be used. In this case, words such as trumpet-shaped or trumpet-shaped do not limit the shape of the keyhole 147.

[0149] To summarize the above, the laser processing apparatus 31, 41 makes the lateral aberration at the paraxial focus 117 of the laser processing head 116 proportional to the power of the divergence angle of the laser 144, and sets the value of the power exponent β to a value less than 3, thereby providing an aberration larger than the spherical aberration. As a result, the laser processing apparatus 31, 41 can obtain a higher effect of reducing the spatter 146, and can achieve high-quality processing.

[0150] In formula (3), by using higher-order aspheric coefficients A j Compared with the case where only A4 is used as the aspheric coefficient, it is easier to make the lateral aberration ΔY proportional to the β-th power of the divergence angle θ. j The range of the value of the power exponent β that can easily make the lateral aberration ΔY proportional to the βth power of the divergence angle θ is, for example, 2.5≤β≤3.5. Therefore, for example, when the value of the power exponent β is greater than 2.5 and less than 3, a higher effect of reducing the spatter 146 can be obtained, and higher quality processing can be achieved.

[0151] exist Fig.15 , the case where the power exponent β is 3 and the case where the power exponent β is less than 3 are described, but the power exponent β may be greater than 3 in order to obtain the best intensity of the peripheral light beam 161 corresponding to the processing object 143. Therefore, for example, when the power exponent β is greater than 3 and less than 3.5, the best intensity of the peripheral light beam 161 corresponding to the processing object 143 can be obtained. When the power exponent β is set to 3, the same lateral aberration as the case of spherical aberration can be generated at the paraxial focus 117 of the laser processing head 116.

[0152] Fig.17 : is a diagram showing an example of the relationship between the aspheric coefficient and the lateral aberration in Embodiment 1. Fig.17 In FIG. 1 , a graph showing the relationship between the fourth-order aspheric coefficient A4 in equation (3) and the lateral aberration ΔY at the paraxial focus 117 of the laser processing head 116 when the divergence angle θ is set to a constant θ2 is shown. Fig.17 In the figure, a solid line 197 indicates that the optical magnification M of the processing optical system 114 is equal to f f / f c The relationship between the aspheric coefficient A4 and the lateral aberration ΔY when the optical magnification M is set to 1. The dotted line 198 represents the relationship between the aspheric coefficient A4 and the lateral aberration ΔY when the optical magnification M is set to 2. The single-point dashed line 199 represents the relationship between the aspheric coefficient A4 and the lateral aberration ΔY when the optical magnification M is set to 4.

[0153] Fig.18 It means about having Fig.17 171 and 173. The parameters are the aspheric coefficients A4 and A2 of the aberration lenses 171 and 173. k , the aberration ΔY generated by the processing optical system 114 OAnd lateral aberration ΔY. Let k be an even number greater than 6. Let lateral aberration ΔY be lateral aberration generated at the paraxial focus 117 of the laser processing head 116 after the laser light 144 passes through the aberration lenses 171 , 173 and the processing optical system 114 .

[0154] exist Fig.18 In order to explain with a simple example, let the aspheric coefficient A k is zero, and ΔY O is zero. O Zero means that no aberration is generated by the processing optical system 114, or the aberration generated by the processing optical system 114 is small to a negligible degree. The value of the aspheric coefficient A4 in the aberration lens 171 is a positive value. The lateral aberration ΔY when the aberration lens 171 is used is a negative lateral aberration. The value of the aspheric coefficient A4 in the aberration lens 173 is a negative value. The lateral aberration ΔY when the aberration lens 173 is used is a positive lateral aberration.

[0155] like Fig.17 As shown, the aspheric coefficient A4 and the lateral aberration ΔY are in a proportional relationship. In addition, by changing the optical magnification M, the slope of the curve representing the relationship between the aspheric coefficient A4 and the lateral aberration ΔY changes. The slope of the curve is in a proportional relationship with the inverse of the optical magnification M. The relationship between the aspheric coefficient A4 and the lateral aberration ΔY is represented by the following formula (5).

[0156] [Number 5]

[0157]

[0158] Next, a case where aberration may be generated by the processing optical system 114, that is, ΔY O When the value is other than zero. Fig.19 ΔY is an aberration generated by the processing optical system 114 when the convex aberration lens 171 is used in Embodiment 1. O A diagram showing an example of the relationship with the aspherical coefficient A4. Fig. 20 ΔY is an aberration generated by the processing optical system 114 when the convex aberration lens 171 is used in Embodiment 1. O A diagram showing an example of the relationship between φ and the movement amount d of the aberration lens 171. Fig.21 This is a diagram showing an example of the relationship between the aspheric coefficient A4 and the movement amount d of the aberration lens 171 when the convex aberration lens 171 is used in Embodiment 1. Fig. 22 ΔY is an aberration generated by the processing optical system 114 when the concave aberration lens 173 is used in the first embodiment. O A diagram showing an example of the relationship with the aspherical coefficient A4. Fig.23ΔY is an aberration generated by the processing optical system 114 when the concave aberration lens 173 is used in the first embodiment. O A diagram showing an example of the relationship between the amount of movement d of the aberration lens 173.

[0159] Fig.24 This is a diagram showing an example of the relationship between the aspheric coefficient A4 and the movement amount d of the aberration lens 173 when the concave aberration lens 173 is used in Embodiment 1. Fig.25 It means about having Figures 19 to 21 The relationship shown in the characteristics of the aberration lens 171 and having as Figure 22 to Figure 24 A diagram showing an example of the relationship between the characteristics of the aberration lens 173 and the parameters thereof.

[0160] exist Fig.25 In the example shown, Fig.18 Similarly, let the aspheric coefficient A k is zero. Fig.25 In the figure, the aberration ΔY generated by the processing optical system 114 is assumed to be O The lateral aberration ΔY when the aberration lens 171 is used is assumed to be a constant value that is a negative value. The lateral aberration ΔY when the aberration lens 173 is used is assumed to be a constant value that is a positive value.

[0161] exist Fig.19 and Fig. 22 , the aberration ΔY generated by the processing optical system 114 is shown. O The relationship between the aspheric coefficient A4 and the Fig.19 As shown in the figure, when the aspheric coefficient A4 is zero, no aberration is caused by the aberration lens 171, ΔY O =ΔY. Fig. 22 As shown in FIG. 1 , when the aspheric coefficient A4 is zero, no aberration is caused by the aberration lens 173, and ΔY O =ΔY. That is, when the aspheric coefficient A4 is zero, the aberration ΔY generated by the processing optical system 114 is O It is equal to the lateral aberration ΔY at the paraxial focus 117 of the laser machining head 116 .

[0162] like Fig.19 As shown, with the aberration ΔY generated by the processing optical system 114 O As the aspheric coefficient A4 in the aberration lens 171 increases, Fig. 22 As shown, with the aberration ΔY generated by the processing optical system 114 O becomes larger, and the aspheric coefficient A4 in the aberration lens 173 becomes larger.

[0163] exist Fig. 20 and Fig.23 , the aberration ΔY generated by the processing optical system 114 is shown. O A graph showing the relationship between the amount of movement d of the aberration lenses 171 and 173. Here, it is assumed that the lateral aberration ΔY at the paraxial focus 117 of the laser processing head 116 is equal when the divergence angle θ is θ1 and the position of the aberration lenses 171 and 173 on the optical axis is P1 and when the divergence angle θ is θ2 and the position of the aberration lenses 171 and 173 on the optical axis is P2. In this case, the amount of movement d is the distance between the position P1 and the position P2. That is, d=|P1-P2| holds.

[0164] like Fig. 20 As shown, with the aberration ΔY generated by the processing optical system 114 O The value of is close to the value of the lateral aberration ΔY, and the movement amount d becomes larger. Fig.23 As shown, with the aberration ΔY generated by the processing optical system 114 O The value of is close to the value of the lateral aberration ΔY, and the movement amount d becomes larger. Fig. 20 As shown in the figure, when the lateral aberration ΔY is a negative lateral aberration, the larger the aberration ΔY generated by the processing optical system 114 is .... O , the smaller the movement amount d. Fig.23 As shown in the figure, when the lateral aberration ΔY is positive, the smaller the aberration ΔY generated by the processing optical system 114 is .... O The smaller the movement amount d, the smaller the movement amount d. The smaller the movement amount d, the smaller the movable range of the movable mechanism 172 can be, and the smaller the movable mechanism 172 can be.

[0165] The general processing optical system 114 makes the aberration ΔY O To zero, or to make the aberration ΔY O In contrast, in Fig. 20 and Fig.23 In the case of the relationship shown in FIG. 1 , by making the aberration ΔY generated by the processing optical system 114 O The sign of the lateral aberration ΔY at the paraxial focus 117 of the laser processing head 116 is opposite to that of the lateral aberration ΔY, and the movement amount d can be reduced. That is, when the lateral aberration ΔY is a positive value, the aberration ΔY is O When the lateral aberration ΔY is negative, the aberration ΔY is set to a negative value. O Just set it to a positive value.

[0166] exist Fig.21 and Fig.24 , a graph showing the relationship between the aspheric coefficient A4 and the movement amount d of the aberration lenses 171 and 173 is shown. Fig.21 The relationship shown is based on Fig.19The relationship shown and Fig. 20 The relationships shown are derived. Fig.24 The relationship shown is based on Fig. 22 The relationship shown and Fig.23 The relationships shown are derived.

[0167] like Fig.21 As shown in FIG. 1 , as the positive value of the aspheric coefficient A4 increases, the movement amount d decreases. Fig.24 As shown in FIG. 1 , as the negative value of the aspheric coefficient A4 decreases, the shift amount d decreases. Fig.21 and Fig.24 As the absolute value of the aspheric coefficient A4 increases, the movement amount d decreases. Therefore, by increasing the absolute value of the aspheric coefficient A4, the movable range of the movable mechanism 172 can be reduced, and the movable mechanism 172 can be miniaturized.

[0168] exist Figures 17 to 25 In order to explain with a simple example, the aspheric coefficient A is k is set to zero, but in embodiment 1, the aspheric coefficient A k It can also be a value other than zero. k For values ​​other than zero, a wider divergence angle range θ r =θ1-θ2 to achieve the divergence angles θ1 and θ2 that make the lateral aberration ΔY at the paraxial focus 117 of the laser processing head 116 equal. By making the aspheric coefficient A k The aberration lenses 171 and 173 with a value other than zero are moved in the direction of the optical axis to achieve a wider divergence angle range θ. r The beam shape of the laser beam 144 at the irradiation position is made the same. As a result, the laser processing devices 31 and 41 can be used in a larger divergence angle range θ. r Achieve stable processing. Divergence angle range θ r For example, the divergence angle range may be the same as the divergence angle range of the laser 144 emitted from the optical fiber 142. For example, when the divergence angle range of the laser 144 is 50 mrad to 110 mrad, the divergence angle range θ may be set to r =110mrad-50mrad=60mrad.

[0169] In Embodiment 1, the aberration optical system is set to be aberration lenses 171, 173, and 174 that are single lenses, but the present invention is not limited thereto. The aberration optical system may include a plurality of lenses. Alternatively, the aberration optical system may include optical elements other than lenses.

[0170] Implementation method 2.

[0171] In Embodiment 2, three configuration examples of a laser processing apparatus will be described. In Embodiment 2, the same reference numerals are given to the same configuration elements as those in Embodiment 1, and configurations different from those in Embodiment 1 will be mainly described.

[0172] Fig.26 1 is a diagram showing the structure of a laser processing device 51 according to a first example of Embodiment 2. The laser processing device 51 is provided with an aberration lens 175 instead of the aberration lens 171, which is different from the Fig.10 The laser processing device 31 shown. Except for this point, the laser processing device 51 is the same as the laser processing device 31. In the first example of the second embodiment, the aberration optical system is an aberration lens 175 which is a single lens. The aberration lens 175 is a convex lens having a convex surface which is a spherical surface.

[0173] The laser processing head 116 includes a movable mechanism 172 for moving the aberration lens 175 in the direction of the optical axis. The laser processing device 51 includes a control device for controlling the movable mechanism 172. The movement of the aberration lens 175 achieved by the movable mechanism 172 is the same as that of the aberration lens 171. The aberration lens 175 having a spherical surface can be easily manufactured compared to a lens having an aspherical surface. In the first example, the processing optical system 114 is an optical system that does not generate aberrations. The processing optical system 114 may also be an optical system that generates aberrations that are small enough to be ignored. In addition, in Fig.26 In the figure, the processing object 143 and the control device are omitted.

[0174] The aberration lens 175 has, for example, a first surface 201 which is a spherical and convex surface and a second surface 202 which is a spherical and convex surface. The first surface 201 and the second surface 202 have different curvatures C. The aberration lens 175 has no optical power for the light on the central axis. The central axis of the aberration lens 175 coincides with the optical axis of the laser light 144 passing through the aberration lens 175. Fig.26 In the laser processing device 51 shown, the first surface 201 is the incident surface for the laser 144, and the second surface 202 is the exit surface for the laser 144. In addition, the term "no optical power for the light on the central axis" includes the case where the optical power for the light on the central axis is negligibly small.

[0175] Since the aberration lens 175 has no refractive power for the light on the central axis, the position of the paraxial focus 117 of the laser processing head 116 changes little even if the aberration lens 175 is moved by the movable mechanism 172. Thus, the laser processing device 51 can stabilize the irradiation position of the laser beam 144.

[0176] When the curvature of the first surface 201 is set to C1, the curvature of the second surface 202 is set to C2, the central thickness of the aberration lens 175 is set to t, and the refractive index of the aberration lens 175 is set to n, the relationship between the curvatures C1 and C2 when there is no optical power for the light rays on the central axis is expressed by the following formula (6). In addition, let C1≠0 and C2≠0.

[0177] [Equation 6]

[0178]

[0179] Regarding the combination of the curvatures C1 and C2, it can be selected to satisfy formula (6) and can obtain the desired lateral aberration at the paraxial focus 117 of the laser processing head 116.

[0180] Fig. 27 is a diagram for explaining the structure of the aberration optical system in Embodiment 2. In Fig. 27 it shows an example of the shape and curvatures C1 and C2 of the aberration lens 175 as the aberration optical system. The curvatures C1 and C2 are each constant and do not depend on r. Also, from formula (6), it can be seen that C1 < C2 holds. In Fig.26 and Fig. 27 it shows examples where the curvatures C1 and C2 are each positive values, but the curvatures C1 and C2 can also be each negative values.

[0181] By moving the aberration lens 175 in the direction of the optical axis using the movable mechanism 172, the laser processing apparatus 51 can cause the lasers 144 with different divergence angles θ to generate the same lateral aberration ΔY2 at the paraxial focus 117 of the laser processing head 116. Thereby, the laser processing apparatus 51 can reduce the change in the beam shape at the irradiation position and can achieve stable processing.

[0182] The aberration lens 175 may also have an optical power on the central axis within a range where the position of the paraxial focus 117 of the laser processing head 116 does not change significantly. Or, the aberration lens 175 may have an optical power in the central region 185 in the same manner as the aberration lens 174 shown in Fig.14 (D) thereof. In the case of having an optical power in the central region 185, the absolute value of the optical power in the central region 185 of the aberration lens 175 is, for example, 1 / 10 or less of the optical power of the collimating lens 112. The absolute value of the optical power in the central region 185 of the aberration lens 175 may also be 1 / 100 or less of the optical power of the collimating lens 112.

[0183] When the focal length f of the collimating lens 112 cWhen the distance is 200 mm, the focal length of the collimating lens 112 is equivalent to 5D, so the absolute value of the focal length in the central area 185 of the aberration lens 175 is, for example, 0.5D or less, which is equivalent to 1 / 10 of 5D or less. The absolute value of the focal length in the central area 185 of the aberration lens 175 may also be 0.05D or less, which is equivalent to 1 / 100 of the focal length of the collimating lens 112 or less.

[0184] The curvature C1 of the first surface 201 and the curvature C2 of the second surface 202 may be set so that the combined focal length f of the combination of the aberration lens 175 and the collimator lens 112 is e Equal to the focal length f of the collimating lens 112 c Hereinafter, the combination of the aberration optical system and the collimation optical system is referred to as a combined collimation optical system. Here, the combined collimation optical system is a combined collimation lens which is a combination of the aberration lens 175 and the collimation lens 112 .

[0185] About the composite focal length f e , by finding the ray tracing matrix F from the output end of the optical fiber 142 to the combined collimating lens e And the ray tracing matrix F e The ray tracing matrix F is expressed by the following equation (7): e .

[0186] [Number 7]

[0187]

[0188] In equation (7), it is assumed that the collimating lens 112 has a focal length of f c Let d0 be the distance between the exit end of the optical fiber 142 and the first surface 201 of the aberration lens 175. Let d1 be the distance between the second surface 202 of the aberration lens 175 and the collimating lens 112.

[0189] The combined focal length f of the collimating lens e Equal to the focal length f of the collimating lens 112 c When , the curvatures C1 and C2 satisfy the following equation (8). In addition, it is assumed that C1≠0, C2≠0.

[0190] [Number 8]

[0191]

[0192] In this case, the distance d1 and the focal length f can also be c The laser processing device 51 is provided with a laser processing device that satisfies f e =f cThe combined collimating optical system can obtain the desired aberration at the paraxial focus 117 of the laser processing head 116, and can achieve stable processing. In addition, in the above description, it is assumed that the collimating lens 112 is a thin lens, but for example, it can also be assumed that the collimating lens 112 is a plano-convex lens or a lens that minimizes spherical aberration.

[0193] exist Fig.26 In the figure, the aberration lens 175 in which both the first surface 201 and the second surface 202 are spherical surfaces is shown as an example, but the aberration lens 175 is not limited to the first surface 201 and the second surface 202 being spherical surfaces. The aberration lens 175 can also be formed by replacing the first surface 201 or the second surface 202 with an aspherical surface represented by formula (1). For example, when the aberration lens 175 has a first surface 201 replaced with an aspherical surface and a second surface 202 as a spherical surface, the curvature of the first surface 201 is replaced from the curvature C1 to the curvature C0 represented by formula (1). In this case, the laser processing device 51 can also reduce the change in the position of the paraxial focus 117 of the laser processing head 116 when the aberration lens 175 is moved by the movable mechanism 172, and can stabilize the irradiation position of the laser 144.

[0194] In addition, by replacing the first surface 201 or the second surface 202 with an aspherical surface, it is possible to easily obtain desired aberrations at the paraxial focus 117 of the laser processing head 116. For example, when both the first surface 201 and the second surface 202 are spherical surfaces, if the absolute value of the lateral aberration at the paraxial focus 117 of the laser processing head 116 is to be increased, the absolute values ​​of the curvatures C1 and C2 become larger. In contrast, by replacing one of the first surface 201 and the second surface 202 with an aspherical surface, it is possible to prevent the absolute values ​​of the curvatures C1 and C2 from becoming larger, and it is possible to easily obtain desired aberrations.

[0195] Fig.28 1 is a diagram showing a structure of a laser processing device 61 according to a second example of Embodiment 2. The laser processing device 61 is provided with an aberration lens 176 instead of the aberration lens 175, which is different from the Fig.26 The laser processing device 51 shown. Except for this point, the laser processing device 61 is the same as the laser processing device 51. The aberration lens 176 is an aberration optical system including a plurality of spherical lenses.

[0196] Fig.28The aberration lens 176 shown has a first lens 211 and a second lens 212. The first lens 211 is a plano-concave spherical lens having a spherical and concave incident surface and a planar exit surface. The second lens 212 is a plano-convex spherical lens having a spherical and convex incident surface and a planar exit surface. In the second example, by using a plano-concave spherical lens and a plano-convex spherical lens with high versatility for the aberration lens 176, the optical system of the laser processing head 116 can be easily constructed.

[0197] The laser processing head 116 includes a movable mechanism 172 for moving the aberration lens 176 in the direction of the optical axis. The laser processing device 61 includes a control device for controlling the movable mechanism 172. The movement of the aberration lens 176 by the movable mechanism 172 is the same as that of the aberration lens 171. In the second example, the processing optical system 114 is an optical system that does not generate aberration. The processing optical system 114 may also be an optical system that generates aberrations that are small enough to be ignored. In addition, in Fig.28 In the figure, the processing object 143 and the control device are omitted.

[0198] The curvature of the incident surface of the first lens 211 is set to C3, and the curvature of the incident surface of the second lens 212 is set to C4. The relationship between the curvatures C3 and C4 when there is no optical power for the light on the central axis is expressed by the following formula (9). The so-called no optical power for the light on the central axis includes the case where the optical power for the light on the central axis is small to a negligible degree. In addition, it is assumed that C3≠0, C4≠0.

[0199] [Number 9]

[0200]

[0201] Here, t3 is the center thickness of the first lens 211, and d2 is the distance between the exit surface of the first lens 211 and the second lens 212. The combination of curvatures C3 and C4 can be selected to satisfy equation (9) and obtain the desired lateral aberration at the paraxial focus 117 of the laser processing head 116.

[0202] Since the aberration lens 176 does not have the optical power for the light on the central axis, even if the aberration lens 176 is moved by the movable mechanism 172, the change in the position of the paraxial focus 117 of the laser processing head 116 is small. Thus, the laser processing device 61 can stabilize the irradiation position of the laser 144. The laser processing device 61 can move the aberration lens 176 while maintaining the state of not having the optical power for the light on the central axis by moving the aberration lens 176 in the direction of the optical axis while keeping the distance d2 constant. The laser processing device 61 can reduce the change in the beam shape at the irradiation position and realize stable processing.

[0203] The curvature C3 of the incident surface of the first lens 211 and the curvature C4 of the incident surface of the second lens 212 may be set so that the combined focal length f of the combination of the aberration lens 176 and the collimating lens 112 is e2 Equal to the focal length f of the collimating lens 112 c In the second example, the combined collimating optical system is assumed to be a combined collimating lens which is a combination of the aberration lens 176 and the collimating lens 112 .

[0204] About the composite focal length f e2 , by finding the ray tracing matrix F from the output end of the optical fiber 142 to the combined collimating lens e2 And the ray tracing matrix F e2 The inverse of the 2 row and 1 column components of is multiplied by -1. e2 , which can be combined with the ray tracing matrix F shown in equation (7) e Here, the calculation of the ray tracing matrix F is omitted. e2 Description of the method.

[0205] Laser processing device 61 in f e =f c Even in the case of the aberration lens 176 being moved in the direction of the optical axis while keeping the distance d2 constant, the aberration lens 176 can be moved while maintaining a state of not having an optical power for the light on the central axis. e =f c The combined collimating optical system can obtain the desired aberration at the paraxial focus 117 of the laser processing head 116, and can achieve stable processing.

[0206] exist Fig.28 In the second example, the aberration lens 176 including the first lens 211 having a concave incident surface and the second lens 212 having a convex incident surface is shown as an example, but the structure of the aberration lens 176 in the second example is not limited thereto. The exit surface of the first lens 211 may be a convex surface, and the exit surface of the second lens 212 may be a concave surface.

[0207] Fig.29 1 is a diagram showing a structure of a laser processing device 71 according to a third example of Embodiment 2. The laser processing device 71 is provided with an aberration lens 177 instead of the aberration lens 175, which is different from the Fig.26 The laser processing device 71 is similar to the laser processing device 51 except for this point. The aberration lens 177 is an aberration optical system including a plurality of spherical lenses.

[0208] Fig.29The aberration lens 177 shown has a first lens 213 and a second lens 214. The first lens 213 is a plano-concave spherical lens having a plane incident surface and a spherical and concave exit surface. The second lens 214 is a plano-convex spherical lens having a plane incident surface and a spherical and convex exit surface. In the third example, by using a plano-concave spherical lens and a plano-convex spherical lens with high versatility for the aberration lens 177, the optical system of the laser processing head 116 can be easily constructed.

[0209] The laser processing head 116 includes a movable mechanism 172 for moving the aberration lens 177 in the direction of the optical axis. The laser processing device 71 includes a control device for controlling the movable mechanism 172. The movement of the aberration lens 177 by the movable mechanism 172 is the same as that of the aberration lens 171. In the third example, the processing optical system 114 is an optical system that does not generate aberration. The processing optical system 114 may also be an optical system that generates aberrations that are small enough to be ignored. In addition, in Fig.29 In the figure, the processing object 143 and the control device are omitted.

[0210] Laser processing device 71 and Fig.28 The laser processing device 61 shown in the figure can stabilize the irradiation position of the laser beam 144. The laser processing device 71 can reduce the change of the beam shape at the irradiation position and realize stable processing.

[0211] exist Fig.29 In the third example, the aberration lens 177 including the first lens 213 having a concave exit surface and the second lens 214 having a convex exit surface is shown as an example, but the structure of the aberration lens 177 in the third example is not limited thereto. The incident surface of the first lens 213 may be a convex surface, and the incident surface of the second lens 214 may be a concave surface.

[0212] exist Fig.28 and Fig.29 , an example is shown in which the aberration lenses 176 and 177 each include two spherical lenses, but the aberration lenses 176 and 177 may each include three or more spherical lenses. The lenses constituting the aberration lenses 176 and 177 are not limited to plano-concave spherical lenses or plano-convex spherical lenses. Among the lenses constituting the aberration lenses 176 and 177, the spherical lens may also be a biconvex spherical lens, a biconcave spherical lens, a convex meniscus lens, or a concave meniscus lens.

[0213] The curvatures of the first lenses 211 and 213 and the curvatures of the second lenses 212 and 214 can also be calculated based on the ray tracing matrix F from the incident surface of the first lenses 211 and 213 to the exit surface of the second lenses 212 and 214. e3 In this case, the ray tracing matrix F is obtained. e3, determine the curvature of the first lens 211, 213 and the curvature of the second lens 212, 214 so that the ray tracing matrix F e3 The 2 row and 1 column components are zero, and the ray tracing matrix F e3 The 2 row and 2 column components are 1.

[0214] By making the ray tracing matrix F e3 The 2 row and 1 column components are zero, and the ray tracing matrix F e3 The 2 row and 2 column components of are 1, and even if the aberration lenses 176 and 177 are moved in the direction of the optical axis by the movable mechanism 172, the position of the paraxial focus 117 of the laser processing head 116 does not change, and stable processing can be achieved. For example, by setting the first lens 211, 213 or the second lens 212, 214 as a convex meniscus lens or a concave meniscus lens, the ray tracing matrix F e3 The 2 rows and 1 column components are zero, and the ray tracing matrix F e3 The 2 row and 2 column components are 1.

[0215] Implementation method 3.

[0216] In Embodiment 3, two configuration examples of a laser processing apparatus will be described. In Embodiment 3, the same reference numerals are given to the same configuration elements as those in Embodiment 1 or 2, and configurations different from Embodiment 1 or 2 will be mainly described.

[0217] Fig.30 FIG. 1 is a diagram showing the structure of a laser processing device 81 according to a first example of Embodiment 3. The laser processing head 116 of the laser processing device 81 includes Fig.10 The laser processing device 31 shown in the figure has the same structure as the laser processing head 116, but also includes a first bending mirror 301, a second bending mirror 302, a monitoring lens 303, and a light detection unit 304. By providing the laser processing head 116 with the first bending mirror 301, the second bending mirror 302, the monitoring lens 303, and the light detection unit 304, the state of the processing object 143 and the state of the molten metal 151 can be observed. Fig.30 In FIG. 1 , illustration of the object to be processed 143 and a control device for controlling the movable mechanism 172 is omitted.

[0218] The first bending mirror 301 and the second bending mirror 302 are arranged on an optical path between the collimating lens 112 and the condensing lens 113. The first bending mirror 301 reflects the laser light 144 that has passed through the collimating lens 112 toward the second bending mirror 302. The second bending mirror 302 reflects the laser light 144 that has entered from the first bending mirror 301 toward the condensing lens 113. The condensing lens 113 receives the laser light 144 that has been reflected by the second bending mirror 302.

[0219] The reflection surface of the second bending mirror 302 is provided with a coating for reflecting the laser light 144 and transmitting the light 305 incident on the laser processing head 116 from the processing object 143. The second bending mirror 302 is, for example, a dichroic mirror. The light 305 incident on the laser processing head 116 from the processing object 143 and passing through the focusing lens 113 is incident on the second bending mirror 302. The light 305 passing through the second bending mirror 302 is focused on the light detection unit 304 by the monitoring lens 303.

[0220] The light detection unit 304 is, for example, an imaging device. The imaging device is, for example, a camera having a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. By imaging the object 143 using the imaging device, the state of the object 143 and the state of the molten metal 151 can be observed. The light detection unit 304 may also be a light detector such as a photodiode.

[0221] The focusing lens 113, for example, does not generate aberration or generates aberration that is negligible. When the light detection unit 304 is an image pickup device, by eliminating the aberration of the focusing lens 113, the light 305 can be focused to the image pickup device without aberration. Thus, an image without blur or distortion can be obtained using the image pickup device. In this case, the lateral aberration ΔY2 generated at the paraxial focus 117 of the laser processing head 116 is generated by the collimating lens 112 or the aberration lens 171, or both the collimating lens 112 and the aberration lens 171.

[0222] exist Fig.30 , an example in which the laser processing head 116 includes the aberration lens 171 is shown. However, the laser processing head 116 may also include any one of the above-mentioned aberration lenses 173 , 174 , 175 , 176 , and 177 instead of the aberration lens 171 .

[0223] The laser processing device 81 may also include an illumination light source for illuminating the processing object 143. The illumination light source may be a light source such as a light emitting diode (LED) or a laser diode (LD). By illuminating the processing object 143 with the illumination light source, the state of the processing object 143 or the state of the molten metal 151 can be observed more easily.

[0224] Fig.313 is a diagram showing the structure of a laser processing device 91 involved in a second example of Embodiment 3. The control device 310 of the laser processing device 91 controls the movable mechanism 172. When the light detection unit 304 is a camera device, the control device 310 analyzes the image output from the camera device and controls the movable mechanism 172 based on the analysis result. The control device 310 controls the movable mechanism 172 to move the aberration lens 171 to the optimal position on the optical axis. When the light detection unit 304 is a photodetector, the control device 310 controls the movable mechanism 172 based on the light signal detected by the photodetector. As a control method based on the light signal, for example, feedback control can also be used. In addition, the control device 310 can also control the movable mechanism 172 by combining a control method such as feedforward control. The laser processing device 91 can maintain stable processing by using the control device 310 to continuously control the aberration lens 171 to the optimal position on the optical axis.

[0225] exist Fig.31 , an example in which the laser processing head 116 includes the aberration lens 171 is shown. However, the laser processing head 116 may include any one of the above-mentioned aberration lenses 173, 174, 175, 176, and 177 instead of the aberration lens 171. Fig.31 , an example is shown in which the light detection unit 304 is arranged coaxially with the laser 144, but the light detection unit 304 may not be arranged coaxially with the laser 144. When the light detection unit 304 is not arranged coaxially with the laser 144, for example, a plurality of light detectors serving as the light detection unit 304 may be arranged non-coaxially. In this case, the laser processing device 91 controls the movable mechanism 172 based on the optical signals from the plurality of light detectors.

[0226] Next, a description will be given of hardware that realizes the control device 310 according to Embodiment 3. The control device 310 is realized by a processing circuit. The processing circuit may be a circuit in which a processor executes software, or may be a dedicated circuit.

[0227] In the case where the processing circuit is implemented by software, the processing circuit is, for example, Fig.32 The control circuit shown. Fig.32 3 is a diagram showing a configuration example of a control circuit 320 according to Embodiment 3. The control circuit 320 includes an input unit 321, a processor 322, a memory 323, and an output unit 324. The input unit 321 is an interface circuit that receives data input from outside the control circuit 320 and provides the data to the processor 322. The output unit 324 is an interface circuit that sends data from the processor 322 or the memory 323 to the outside of the control circuit 320.

[0228] The processing circuit is Fig.32In the case of the control circuit 320 shown, the control device 310 is realized by software, firmware, or a combination of software and firmware. Software or firmware is described as a program, which is stored in the memory 323. In the processing circuit, each function is realized by the processor 322 reading the program stored in the memory 323 and executing it. That is, the processing circuit is equipped with a memory 323 for storing a program for executing the processing of the control device 310 in the end. In addition, it can also be said that these programs cause the computer to execute the process and method of the control device 310.

[0229] The processor 322 is a CPU (Central Processing Unit, also called a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor). Equivalent to the memory 323 are: non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), magnetic disks, floppy disks, optical disks, high-density disks, mini disks, or DVDs (Digital Versatile Discs).

[0230] Fig.32 This is an example of hardware in which each component is realized by a general-purpose processor 322 and a memory 323 , but each component may be realized by a dedicated hardware circuit. Fig.33 This is a diagram showing a configuration example of a dedicated hardware circuit 325 according to the third embodiment.

[0231] The dedicated hardware circuit 325 includes an input unit 321, an output unit 324, and a processing circuit 326. The processing circuit 326 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit formed by combining them. Each function of the control device 310 can be implemented by the processing circuit 326 according to the function, or each function can be summarized and implemented by the processing circuit 326. In addition, the control circuit 320 and the hardware circuit 325 can be combined to implement the control device 310.

[0232] The structures shown in the above embodiments represent an example of the contents of the present disclosure. The structures of the embodiments can be combined with other known technologies. The structures of the embodiments can also be appropriately combined with each other. Within the scope of not departing from the gist of the present disclosure, a part of the structure of the embodiments can be omitted or changed.

[0233] (Explanation of Reference Numerals)

[0234] 21, 31, 41, 51, 61, 71, 81, 91: laser processing device; 111: point light source; 112: collimating lens; 113: focusing lens; 114: processing optical system; 116: laser processing head; 117: paraxial focus; 118, 119, 145, 165, 167, 195, 196: contour; 120: forward direction; 121, 122: light; 141: laser oscillator, 142: optical fiber; 143: processing object; 144: laser; 146: splash; 147: keyhole; 148: front wall; 149: rear wall; 150 : Molten metal flow; 151: Molten metal; 152: Bottom; 153: Surface; 154: Reference plane; 155: Opening; 160: Main beam; 161: Peripheral beam; 162: Evaporation reaction force; 163: Metal vapor; 166: Peripheral beam width; 171, 173, 174, 175, 176, 177: Aberration lens; 172: Movable mechanism; 180: Plano-convex spherical lens; 181, 183, 201: First surface; 182, 184, 202: Second surface; 185: Central area; 186: Peripheral area; 190, 191, 192,

[0235] 193, 194, 197, 198, 199: lines; 211, 213: first lens; 212, 214: second lens; 301: first bending mirror; 302: second bending mirror; 303: monitoring lens; 304: light detection unit; 305: light; 310: control device; 320: control circuit; 321: input unit; 322: processor; 323: memory; 324: output unit; 325: hardware circuit; 326: processing circuit.

Claims

1. A laser processing head, characterized in that: have: an aberration optical system disposed at a position within a range in which the laser light irradiated toward the object to be processed spreads in a propagation direction of the laser light, and generates aberration; and collimating optical system, propagating the laser light, An area of ​​the aberration optical system whose distance from the central axis of the aberration optical system is less than the boundary value, i.e., a central area, has no optical power, or an absolute value of the optical power is less than 1 / 10 of the optical power of the collimating optical system. The area in the aberration optical system whose distance from the central axis exceeds the boundary value, i.e., the peripheral area, has the following focusing characteristics: when light parallel to the central axis is made incident on the peripheral area, the farther the light is from the central axis, the shorter the distance between the aberration optical system and the focus of the light.

2. The laser processing head according to claim 1, characterized in that: A synthetic focal length of a combination of the aberration optical system and the collimating optical system is equal to a focal length of the collimating optical system.

3. The laser processing head according to claim 1 or 2, characterized in that: The lateral aberration at the paraxial focus of the laser light passing through the laser processing head is proportional to the power of the divergence angle of the laser light. The power exponent of the power is a value less than 3.

4. The laser processing head according to claim 1 or 2, characterized in that: The aberration optical system is a single lens, and the portion of the peripheral area in the incident surface of the single lens where the laser is incident, or the portion of the peripheral area in the exit surface of the single lens where the laser is emitted, is a shape in which the curvature monotonically increases or monotonically decreases as it moves away from the central axis.

5. The laser processing head according to claim 1 or 2, characterized in that: The lateral aberration at the paraxial focus of the laser light passing through the laser processing head is proportional to the power of the divergence angle of the laser light. The power exponent of the power is 3.

6. The laser processing head according to claim 1 or 2, characterized in that: The aberration optical system includes a plurality of spherical lenses.

7. The laser processing head according to any one of claims 1 to 6, characterized in that A light detecting unit is provided, the light detecting unit detecting the light incident on the laser processing head from the processing target object.

8. The laser processing head according to any one of claims 1 to 7, characterized in that A movable mechanism is provided for moving the aberration optical system in the direction of the optical axis of the laser light passing through the aberration optical system.

9. The laser processing head according to any one of claims 1 to 8, characterized in that A focusing optical system is provided for focusing the laser light. The sign of the lateral aberration at the paraxial focus of the laser light is opposite to the sign of the lateral aberration generated by the combination of the collimating optical system and the focusing optical system.

10. A laser processing device, characterized in that: have: a laser oscillator for emitting laser light; and A laser processing head as claimed in any one of claims 1 to 9.

11. A method for manufacturing a metal product, characterized in that: A third metal product is manufactured by irradiating a first metal product and a second metal product with the laser beam having passed through the laser processing head according to any one of claims 1 to 9, and welding the first metal product and the second metal product.

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